The koala population has dropped by about 26% over the past two decades in NSW, according to studies.

"We know that there are around 36,000 koalas left in the state, but we don't know that for sure," NSW Premier Gladys Berejiklian said.

"It would be such a shame if this nationally iconic marsupial did not have its future secured."

The Australian Koala Foundation estimates there may be as few as 43,000 koalas left in the wild, down from a population believed to have numbered more than 10 million prior to the European settlement of the continent in the 18th Century.